After taking the natural logarithm of both sides of Equation 1 twice, the linear regression equation is given as12-13
: Eqn. 2
plane. As far as aluminum castings are concerned, the value of X for relatively low (<1%) probabilities of failure under stress basically relates to m (see 14, 15, 16
The Weibull modulus, m, is the slope of the regression line between Y and the natural logarithm of the UBS, namely X for simplicity, and -mln(σ0
). In congruence, m
is usually taken as a measure of engineering reliability for a given cast product.
) is the Y-intercept in the X-Y
(a)
(b)
Figure 20. In-weld fracture of sample B-C1 after bend testing: (a) Surface of sample, which was in contact with bottom forces; (b) Crack adjacent to the fracture surface.
(a)
(b)
(c)
Figure 21. Regions of porosity located on the fracture surfaces of bend test specimens: (a) B-A1 pore at 700x magnification; (b) B-4 pore at 200x; (c) two pores near edge of B-4 at 100x.
78 International Journal of Metalcasting/Spring 2012
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